WO2011/011799 (Procter and Gamble) discloses violet thiophene dyes containing a anionic group covalently bound to alkoxy groups for use in laundry detergents for whitening textiles.
To obtain other aesthetic colours in the detergent, violet anionic thiophene dyes are mixed with additional dyes. Colour brightness is a key attribute of colour that the consumer desires. Consumers do not like dull colours.